Signaling system



Dec. 1924- 1,519,4 2?

w; c. BEACH SIGNALING SYSTEM Filed Sept. 20, 1921 VAVAV Patented Face. 16, 1924.

UNlTED STATES PATENT @FFlCE.

WILLIAM C. BEACH, OE I-JLGOlIFIE-Izll, NEW dERSEY, ASSIGNGB TO WESTERN ELECTRIC COMPANY, INCORPQRATED, OF NEVT YORK, N. Y., A CORPORAEIGN OF NEW YORK.

SIGNALING- SYSTEM.

Application filed September 20, 1921.

To all '20/ 20'i7L it may concern:

Be it known that 1, WILLIAM C. Enron, a citizen of the United States, residing at Bloomfield, in the county of Essex; State of New Jersey, have invented certain new and useful Improvements in Signaling Sys terns, of which the following is a lull, clear, concise, and exact description.

This invention relates to signaling systems and more particularly to methods and means for transmitting an audible signal to a calling subscribers station to indicate that the called subscribers station is being signaled.

In some circuits of this nature now being used, there is considerable variation in the character of the signal transmitted to the station of the calling subscriber due to variations in the ringing current for signaling the called subscriber, which current is used also to signal the calling subscriber thatthe called subscriber is being signaled.

In some systems, which are now widely used, the audible ringing signal is obtained from the regular ringing current source which is generally of a frequency of approximately 16 cycles per second. The signaling tone is due to the higher harmonic components of audible frequency+-generally the so 'calle'd slot ripples of the ringing machine. These harmonic COHIP'ODHtS, be ing superimposed upon the 16 cycle current, are accordingly subject to modulation twice each cycle or 32 times per second. This results in a characteristic tone wh'iclrha's come to be well known and which differs from that obtained when the tone is supplied without interruption from a separate source. In a copending application, Serial No, 4599,- 101, of- Fhilip Husta, filed September 7, 1921, a circuit arrangement employing a separate source of current for the signaling tone, is disclosed, which is free from the disadvantages outlined above.

It is an object or this invention to provide an improved ringi g tone signal. This is accomplished by mo'cu ating current from the same source from which current for signaling the called subscriber is obtained.

For a more complete understanding of the invention, reference may be had to the following description inconnection with the accompanying drawing, Fig. 1 of which illustrates one embodiment oi the invention.

Serial No. 501,974.

Figs. 2, 3 and 4 of the drawing show, respectively, the wave forms of the output of the ringing generator, of the signaling current transmitted to the calling subscriber in one or the above mentioned systems, and of the signaling current transmitted to the calling subscriber in the embodiment of the invention shown in Fig. 1.

In the drawing, a calling and :1 called subscribers station are shown at A and B, respectively. These may be connected by any well known form of link circuit, such as L, arranged to apply ringing current from a source 1 through an interrupter 2, and a marginal tripping relay 3 to the called subscribers line. For the purpose 0t supply ing ringing tone current, an interrupter 4 is provided which is so connected as to modulate alternating current from the source 1. Current from the source 1 is applied to the primary windings 25 of a transformer 5. Current induced in the second ary windings 0t transformer 5 is filtered through a filtering device composed of coils 2'7 and condensers 28. Filtered current is then applied to the calling line, which simulates the modulation of the audible harmonic components of a 16 cycle ringing currentwave, as explained above.

As shown in Fig. 2, the current produced by the source 1 possesses numerous harmonics which affect the wave for n of such current. As previously mentioned, in one system widely in use, the higher audible harmonics superimposed upon the lS-cyclc current are transmitted to the calling subscriber through a repeating coil similar to repeating coil 21. In such a case the current wave flowing over the calling line assumes in general the form shown in Fig. 3. Although there may be many more hai. monies present in this current only a suiticient number have been shown to illustrate the form produced. This current has been found to produce a distinctive and pleasing tone in the calling subscribers receiver. The 16-cycle current flowing from sou "cc 1 through the interrupter a, repeating coil 25 and the associated apparatus, produces a current wave for transmission to the calling subscriber which assumes the general form shown in Fig. 4. The frequency of the resultant current has been selected to correspond with onc ot the prcdoiuihating higher harmonics and the modulated current produces a tone similar in character to that produced by current of the wave shown in Fig. 3.

It is believed that the invention may be more fully comprehended from the following detailed description. It is assumed that the subscriber at station A desires a connection with the subscriber at station B and that connection with the calling station has been established in the usual manner. The connection is then completed in the well known manner over the link circuit L by an operator inserting a plug 1 1 in jack 15. Relay 16 is operated over a circuit extending from grounded battery, winding of relay 16, normal contacts'of relays 3 and 17, which contacts normally short-circuit the winding of relay 17, sleeve contacts of plug it and ack 15, and resistance 18 to ground. Ringing current is then supplied to the line of station 13 from source 1 over the following path: source 1 of ringing current, collector ring 19, segment 6 and brush 7 of interrupter 2, winding of trippinlg relay 3, lowermost alternate contact of relay 16, ring contacts of plug 14 and jack 15, through the loop of station B, tip contacts of jack 15 and plug 14: and contact 31 of relay 16 to ground.

When the brush 7 of interrupter 2 comes into contact with segment 6, relay 9 is energized through condenser 22. This causes modulated ringing current to be furnished to the calling end of the link circuit at the same time that ringing current is being supplied to the called stat-ion, over a circuit which will now be described.

Assuming that relay 9 is operated, a cir cuit may be traced extending through the source 1 of alternating current, then in parallel, one path extending through the windings of transformer 5 in parallel, contact of relay 9, interrupter 4c, and the other path extending through condenser 32, and thence through the rheostat 34 to ground. The impedance of the first traced circuit from the source 1 is preferably less than the impe lance through the second traced circuit, so that more current flows through the windings 25 than flows through the condenser 32. The purpose of the rheostat 3a is to reduce as desired the amount of current taken from the source 1 for the ringing tone circuit. The values of the condenser 32 and of the windings of the transformer 5 are so chosen that a resonant circuit is formed. Oscillations set up in the resonant circuit tend to strengthen the modulated current which is produced by the interrupter 4:. Current passing through the primary winding of the transformer 5 induces a current in the secondary windings 26 and the flow of current is then as follows: from ground, through the windings 26 of transformer 5 in parallel, through the filtering device including coils 27 and condensers 2S, and thence in parallel, one path extending through the low impedance path through coil 13 to ground, and

the other path extending through contacts 30 of relay 16, and thence through the upper right-hand winding of repeating coil 21 to ground. The function of the filtering device consisting of coils 27 and condensers 28 is to prevent currents without a desired range from passing through to the repeating coil 21.

The impedance of the path for the signaling tone through the resistance 13 is low as compared with the path through the re peating coil 21, and the potential drop across resistance 13 is utilized, as in the aforementioned copending application of Philip Husta, to supply signal tone current to station A. The subscriber at station A will accordingly know that the called station 13 is being signaled and the tone which is heard will, by reason of the periodic modulation by the interrupter 1, be similar to that obtained in existing installations from the audible harmonic components of 16 cycle ringing current.

When the called station answers, relay 3 energizes in the well known manner thereby removing thev shunt from relay 17, whereupon relay 17 operates to shunt relay 16. Relay 16 in releasing, disconnects the signaling current from the called station and the signaling tone current from the calling station.

Inasmuch as the link circuit L, shown in the drawing, is well known in the art and is not part of this invention, only so much thereof as is necessary to an understanding of the invention has been disclosed and described herein. This circuit arrangement employed at stations A and B has been omitted since it may be of any well known type.

What is claimed is:

1. In a telephone system, a calling station, a called station, a source of signaling current, an interrupter for periodically supplying current from said source to signal said called station and another interrupter for periodically supplying current from said source to signal said calling station.

2. In a telephone system, a calling station, a called station, a source of signaling current, a plurality of devices for periodically interrupting the flow of current from said source, and means for supplying current through one of said interrupters to signal said called station and through a plurality of said interrupters to signal said calling station. I

3. In a telephone system, a calling station, a called station, a source of signaling current and a plurality of interrupters, one of said interrupters serving to periodically supply currentfrom said source for signaling one of said stations and cooperating with another of said interrupters to supply current from said source to signal the other of said stations.

4. In a telephone system, a calling station, a called station, a source of signaling current, an interrupter for supplying current from said source to said called station, another interrupter associated With said source, and means controlled by said first mentioned interrupter to control the application of current from said source through said second mentioned interrupter to said calling station.

5. In a telephone system, a calling station, a called station, a source of signaling current, means for applying current from said source to said called line, means comprising an interrupter, a resonant circuit and a filtering device for modulating current from said source, and means for applying said modulated current to said calling line.

6. The method of informing a calling subscriber that signaling current is being supplied to a called substation Which comprises generating a current Wave having a frequency approaching the limit of audibility, modulating said Wave at an audio-frequency rate, and supplying the modulated current Wave to the calling subscriber.

7. A telephone system comprising a calling line, a called line, a source of current, means for modulating current from said source, and means for applying unmodulated current from said source to one of said lines and said modulated current to the other of said lines.

In Witness whereof, I hereunto subscribe my name this 10th day of September, A. D.,

W. C. BEACH. 

